I am getting an error when sending midi data out from an Alesis IO26 interface with SendSX 1.22

My Alesis IO26 interface is hooked up to my PC via a Belkin firewire card (Alesis recommended). I have a .syx file that I need to send out to an outboard piece of audio equipment. I load the .syx file in Bome's SendSX 1.22 and send the file. It transfers slowly, but doesn't quite get to the end... SendSX then issues an error message: "An invalid parameter was passed to a system function".

I double-checked everything, the .syx file, the cables, the sending and receiving gear... and was able to actually upload that very same .syx file using a different midi interface (a rudimentary midi in&out on the SoundBlaster Audigy soundcard on an older computer).

I had successfully transferred midi data in both directions using SendSX and that very same Alesis IO26 interface. Not sure how to interpret the SendSX error message.